A large number of different variants and layer sequences of ultrasonic transducer structures are already known.
European Patent, EP 0 974 814 B1 of the field of the invention describes a coupling element having a bearing surface, respectively contact surface. The coupling element has a cavity for accommodating a piezo element. Arranged between the coupling element and the piezo element is a metal disk. This metal disk is adhered in a plane inclined to the bearing surface and forming a base of the cavity. This construction with integrated metal disk has basically proved itself and is distinguished in comparison to glass- and ceramic disks through its high loadability in the face of variable temperature loading.
In the manufacture of a plurality of layers, such as in EP 0 974 814 B1, attention is to be given that the elements are oriented relative to one another as accurately as possible. Thus, e.g. the metal disk should be oriented as parallel as possible to the ultrasonic transducer. In such case, an adhesive can be utilized. During the curing of the adhesive, a shifting of the individual components can be experienced e.g. due to transport related shaking or for other reasons.
It is, consequently, of interest to achieve an as fast as possible fixing of the individual components in place. A faster curing of the adhesive e.g. by overdosing of hardener or an increased temperature regimen can, however, lead to stress cracks or otherwise negatively affect the properties of the coupling element or lead to disadvantageous effects (among others, air bubbles) within the adhesive layers. In these cases, the ultrasonic transducer is lacking in quality.
German Patent, DE 10 2012 207 871 A1 discloses the application of a photochemically curable adhesive for affixing an intermediate layer. In this publication, it is, however, explicitly required that the intermediate layer to be affixed should be at least partially transparent. In such case, primarily a full surface curing of the adhesive is assumed, so that, as much as possible, a full surface irradiation is provided. A metal disk, as a heat conduction capable, intermediate layer, as is provided in EP 0 974 814 B1, consequently goes against the concept of DE 10 2012 207 871 A1, since it is not transparent.
Moreover, in German Patent, DE 10 2013 104 542 A1, an ultrasonic transducer element with a coupling layer is described, in which likewise a metal disk is applied.